1. Field of the Invention
The present invention relates to a vehicle driving condition prediction device for predicting the lateral acceleration which will occur when passing through a curve ahead, and to a vehicle driving condition warning device for producing a warning when a predicted lateral acceleration exceeds a specified reference value.
2. Discussion of Related Art
Such automobile navigation system is well known which provides route guidance for the driver of a vehicle. The navigation systems are being installed in an increasing number of vehicles. The navigation system stores road map data, including road shapes and monitors the present position of the vehicle. Therefore, it is possible for the system to recognize that there is a curve ahead before entering the curve. It has been proposed to optimize the vehicle speed when going into a curve using the navigation system. For example, in Japanese Patent Laid-Open Publication No. 5-141979 (JP-A-05141979), the lateral acceleration G while driving through a curve is calculated from the radius of curvature R of the curve ahead and the present vehicle speed. The calculated lateral acceleration G is compared with a predetermined reference value G0. If the lateral acceleration G exceeds the reference value G0, a decision is made at the vehicle should slow down, and a warning is issued.
As the driver reduces the speed in response to the warning, the vehicle speed while entering the curve can be optimized, so that the vehicle can pass through the curve stably.
However, the problem with the above warning system is that a curve warning is troublesome because it is issued even when driving at a safe speed. Further, with other conventional warning devices, a warning tends to be issued when the driver was planning to reduce the speed even without the warning.